Volatile organic compounds (VOC) and semi-volatile organic compounds (SVOC) present on the skin are derived from four processes: glandular secretions from the eccrine, apocrine and sebaceous glands within the skin; exogenous inputs to the skin (such as environmental contamination, topically applied medications as well as personal care and cosmetic formulations); perfusion of compounds from the underlying blood vessels; and the products and by-products of micro-biological metabolism.
Accordingly, the skin profile of VOCs and SVOCs is rich and dynamic and dependent on factors such as the body's metabolic or hormonal state, ingested dietary compounds, variations in the external environment (such as diurnal and seasonal), the particular body site which is sampled, and the bacterial species colonizing the skin surface.
It is becoming increasingly apparent that the information contained in an individual's skin profile of VOCs and SVOCs is a resource of great potential from an analytical perspective. For example, human volatile chemical profiles show promise as a means of diagnosis and health monitoring. Also in non-clinical areas such as cosmetics, toiletries and personal care, understanding of the chemicals related to skin odour could lead to development of more effective deodorant, antiperspirant or fragrance products.
Current skin surface sampling methods are generally focussed on collecting sweat as it exudes from the participant's skin. Such methods are often unsatisfactory since there is little control over the region from which the sweat will be derived. Also thermal stress or intense exercise is usually required in such methods to induce sweating. Therefore the samples are not representative of the range of sweating mechanisms that exist, and the findings cannot necessarily be applied to subjects who might be frail, very young or elderly.
EP 2 109 762 describes an alternative approach in which VOCs are trapped directly from the skin, using a sampler employing a hydrodynamic gas flow to volatilise substances from the skin surface and convey the substances to a collector. The sampler has a gas supply coupled to a hand-held probe that comprises a supply tube, a recovery tube and a skirt. The gas is expelled under pressure through one of the tubes onto the skin surface and recovered through the second tube to the collector. Although this technique eliminates many of the problems involved in sweat sampling, its applicability is limited to the recovery of those substances which are volatile enough to be entrained in the flow of gas.
The object of the present invention is to provide a rapid and non-invasive system of skin surface sampling, which can be used to sample a wide range of compounds (including but not limited to VOCs and SVOCs) from the surface of the skin, and which can be used over all areas of the body. Advantageously, analysis of the samples collected using the system of the invention shows that different body parts may be consistently distinguished, thus allowing rapid, non-invasive chemical mapping of the human body.